Just got back from Orlando. When we went there was the no-carryon rule in full effect, which was challenging to do with a 5 year old. I was able to carry on my laptop bag and smuggle in toys and his iPod and stuff that way. There was no restriction other than the usual ones for electronics. We were there 3 hours before and they let us through security right away. That was a week and a half ago.
Coming back there were lots of people with carry on luggage so it looks like those restrictions have been eased, the signs coming back were saying only one carry on allowed and the same limitations with liquids and gels.
This is where you'll get the most up to date info:
http://www.catsa-acsta.gc.ca/Home.aspx?id=1&lang=en